In the field of infrared imaging, the middle and far infrared region (3-15 micrometers and greater wavelength) of the electromagnetic wavelength spectrum has been of considerable interest to designers of image sensors and the related arts. This is because of the fact that these wavelengths provide relatively large amounts of radiant photon emittance from objects having an average background temperature in the vicinity of 300.degree. Kelvin, or approximately 25.degree. C. and the existing atmospheric window in the 3-5 .mu.m and 8-12 .mu.m regions. Thus, in order for thermal imaging devices to respond satisfactorily to objects having an average temperature in the general vicinity of 300.degree. Kelvin, the radiation sensitive material of the thermal imaging device must receive sufficient energy from such infrared radiation to properly function as an efficient detector.
There are two significant classes of infrared imagers. One of these is the class of quantum detectors, which includes photocathodes such as the bi-alkyl, tri-alkyl and the III-V compound semiconductors. These quantum detectors are not sufficiently responsive to infrared radiation out beyond about 0.9 micrometers to be useful in the infrared region of the electromagnetic wavelength spectrum of interest. In addition to the above photocathodes, photoconductive and photovoltaic semiconductors are also in this class of quantum detectors, and these latter semiconductors include electronic materials such as indium antimonide (for 3-5 .mu.m) and mercury cadmium telluride alloy (for 8-12 .mu.m) which are highly sensitive in the infrared region of the electromagnetic wavelength spectrum. However, because of the relatively narrow band-gaps of these latter materials and the associated problems with dark currents, unless these materials are cooled, it becomes necessary to cool these materials when they are used in infrared imaging systems. The latter requirement results in costly and bulky detector devices.
The second significant class of infrared imagers is the thermal imaging type of detector and includes well-known devices such as thermistors and bolometers which, to my knowledge, have never been utilized in a practical two-dimensional image array. More recently, pyroelectric imagers have been investigated as a low-cost, two-dimensional array suitable for infrared imaging. The relevant prior art in the analogous field of pyroelectric imagers is discussed below.